#include "race.h"
#include <bits/stdc++.h>
using namespace std;
#define int long long
vector<pair<int,int>>adj[200001];
int dsu[200001],sz[200001];
int inbut[200001][2], ll[200001];
map<int,int> store[200001];
int vs[200001],sum[200001];
int ans = INT_MAX, K;
int Find(int x){
if(dsu[x] == x) return x;
else return dsu[x] = Find(dsu[x]);
}
void Unite(int a, int b, int cur_k, int cur_depth){
a = Find(a); b = Find(b);
if(a > b) swap(a,b);
sz[b] += sz[a];
dsu[a] = b;
for(auto s: store[a]){
if(store[b][cur_k - s.first] != 0){
ans = min(ans, s.second - cur_depth + store[b][cur_k - s.first] - cur_depth);
}
}
for(auto s: store[a]){
if(store[b][s.first] == 0 or store[b][s.first] > s.second){
store[b][s.first] = s.second;
}
}
if(store[b][(cur_k - K) / 2 + K] != 0) ans = min(ans, store[b][(cur_k - K) / 2 + K] - cur_depth);
}
void dfs(int x, int par, int depth){
vs[x] = 1;
int vv = 0;
for(auto s: adj[x]){
if(!vs[s.first]){
sum[s.first] += s.second;
sum[s.first] += sum[x];
dfs(s.first, x, depth + 1);
vv++;
}
}
map<int,int>p;
p[sum[x]] = depth;
store[x] = p;
if(vv){
for(auto s: adj[x]){
if(s.first != par){
Unite(x, s.first, 2 * sum[x] + K, depth);
}
}
}
}
signed best_path(signed n, signed k, signed h[][2], signed l[]){
ans = INT_MAX;
for(int i = 1; i <= n; i++){
sum[i] = 0;
vs[i] = 0;
dsu[i] = i;
sz[i] = 1;
adj[i].clear();
}
for(int i = 0; i < n - 1; i++){
h[i][0]++; h[i][1]++;
adj[h[i][0]].push_back({h[i][1], l[i]});
adj[h[i][1]].push_back({h[i][0], l[i]});
}
K = k;
dfs(1, 0, 1);
if(ans == INT_MAX) ans = -1;
return ans;
}
